It's a pretty simple rule, and should be easily learned in elementary school. And once you know the rule, you know it for life and never forget it. Spend 5 minutes thinking about it, learn the rule, and you've got it forever. Once you know the rule, the misuse of "it's" stands out like a sore thumb and you recognize it immediately. It's NOT at all complicated. And if that rule is not important, then none of the grammar rules, spelling and punctuation rules are important either. We really can't pick and choose which grammar rules we decide to follow and which ones we decide are OK to break.